Device for adjusting the relative angle of rotation of a shaft to a drive wheel, especially the camshaft of an internal combustion engine

ABSTRACT

A device for adjusting a relative angle of rotation of a camshaft with respect to a drive wheel of an internal combustion engine utilizes a hydraulic linear motor for actuation. A hydraulic pump with a pump rotor is axially arranged with respect to a longitudinal or adjustment axis of the linear motor.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a device for adjusting a relative angleof rotation of an internal combustion engine camshaft to a drive wheeland, more particularly, to a device in which a hydraulic linear motor isthe actuating arrangement which acts upon an actuating mechanism betweenthe drive wheel and the camshaft.

A device of this general type is known, for example, from EP-A-0 245 791wherein the linear motor interacts with an adjusting mechanism which isused essentially in a front-face recess of the angularly adjustableshaft or camshaft. To this adjusting mechanism, which insignificantlyinfluences the overall length of the internal-combustion engine, thelinear hydraulic motor is assigned on a detachable engine power sectioncover with integrated hydraulic pipes and a control device for utilizingthe space to the front-face end of the adjustable shaft or of theadjusting mechanism. The actuating of the linear hydraulic motor takesplace by a hydraulic system which is separate from the internalcombustion engine and has a separately driven pump.

In addition, a device has been suggested for adjusting the relativeangle of rotation of a shaft to a drive wheel as seen in EP-A-0 363 600in which a rotor of a hydraulic motor, which interacts with theadjusting mechanism of a first adjustable camshaft of aninternal-combustion engine, is acted upon by the delivered flow of ahydraulic pump driven by a second camshaft. In this device, thehydraulic pump and the hydraulic motor, including the hydraulic pipes,form a unit which is assigned to the above-mentioned shafts and which isintegrated in a power section area of the internal-combustion enginewhich is used for driving the shafts.

The present invention is based on the object of combining a device ofthe above-mentioned type with a hydraulic pump such that a compactspace-saving unit is achieved for the structural integration in or onthe internal combustion engine.

This object has been achieved in accordance with the present inventionby such that a hydraulic pump with a pump rotor is arranged coaxiallywith respect to the longitudinal or adjustment axis of the linear motor.

The combination of the hydraulic pump, also known as a hydrostatic pump,and the linear motor in a coaxial arrangement advantageously results ina compact space-saving unit. This unit may, at the same time, serve asthe smallest structural or assembly unit. For achieving a particularlycompact space-saving unit, the linear motor and the hydraulic pump arearranged coaxially with respect to the shaft with the adjustable angleof rotation on a detachably constructed engine power section cover, inwhich case the unit according to the present invention and the enginepower section cover form the next larger structural or assembly unit. Inthis arrangement, parts of the unit according to the present inventioncomprising the hydraulic pump and the linear motor may be an integralcomponent of the engine power section cover. However, a separateconstruction of the unit according to the invention and of the enginepower section cover is also conceivable.

The present invention can be implemented particularly advantageously bythe selection of a radial piston pump and a linear motor constructed asa cylinder/piston unit. The radial piston pump, which is relativelysmall in size but has a sufficient delivered flow and a very highdelivery pressure, therefore promotes the compact construction of theunit, in which the selected construction of the linear motor permits agood constructional adaptation to the selected radial piston pump.Consequently, an especially advantageous embodiment is achieved by thearrangement of the radial piston pump on the engine power section coveron the side of the shaft, in which the pump rotor is disposed in arotatably movable manner on the periphery of the cylinder of the linearmotor. For this extremely compactly configured unit, the drive of theradial piston pump can be achieved elegantly by simple devices byproviding a radial piston pump which is acted upon on the inside and hasa pump housing which is constructed in the engine power section cover,is open on the shaft side, and receives the pump rotor which is in ashaft-side driving connection by way of a plug-in arrangement. When theplug-in arrangement is in parallel to the mounting direction, thesuggested plug-in arrangement considerably promotes the mounting of thestructural or assembly unit according to the invention.

The unit combined according to the invention and comprising a pump rotorof the hydraulic pump or of the radial piston pump which is disposed onthe cylinder of the linear motor in a rotatably movable manner resultsin special advantages with respect to its manufacture and the mountingof details. This results because a separate cylinder of the linearmotor, which is constructed with different outside diameters, isarranged in a step bore of the engine power section cover, and thecylinder, on the shaft side, is equipped with flanged bushes for theslidable bearing of the pump rotor receiving radially displaceabledelivery pistons, in which construction the flanged bushes comprisecontrol openings on the intake side and the delivery side which aredistributed on the periphery for the connection with the inflow andoutflow chambers arranged in the cylinder wall.

The development of functional units of the hydraulic pump or of theradial piston pump in the wall of the cylinder of the linear motorresults in additional simplification because the inflow chamber and theoutflow chamber are each connected with an essentially axially directedduct which is arranged in the cylinder wall, in which this duct isconnected by way of a circumferential groove in the periphery of thecylinder of the linear motor with a pipe arranged in the engine powersection cover. If, in addition, the above-mentioned ducts are arrangedfrom the shaft-side end of the cylinder in its cylinder wall, a flangednut can be assigned to the cylinder on the shaft-side end for the tightsealing of the intake duct and of the delivery duct which also, with itsouter edge area, is used for the axial securing of the flanged bush forthe rotatably movable bearing of the pump rotor on the cylinder.

For radial piston pumps, which are acted upon on the inside and have adelivery piston which is radially movable in the pump rotor, theinteraction of their radially outer ends with a sliding ring arranged inthe pump housing is known. For a pump housing, which is constructed inthe engine power section cover and is open on the shaft side, a separatefixing of the position of this slide ring is not required because, in afurther development embodiment of the present invention, a generatorwheel may be assigned with axial play to the pump housing which is openon the shaft side. In this embodiment, the generator wheel may be, forexample, in a non-rotatable connection with the plug-in arrangement forthe pump rotor. However, the generator wheel may also be constructed inone piece with the pump rotor, in which case the axial assignment of thepump rotor to the pump housing integrated in the engine power sectioncover may be implemented by the plug-in arrangement.

Further embodiments of the invention relate to the arrangement of thehydraulic pipes in the engine power section cover, in whichconfiguration, for avoiding a separate hydraulic system, for example,the intake pipe in the engine power section cover is connected with thelubricant circulating system of the internal-combustion engine. For acontinuous adjustment with a secure holding of the piston in anydesirable position in the angle of rotation, the piston of the linearmotor is constructed as a differential piston, in which pressure lines,which are provided so that this differential piston is acted upon onboth sides, are controlled by a timing valve, in which case hydraulicliquid gradually shut off by the timing valve, by way of a dischargepipe in the engine power section cover which leads out on the side ofthe engine, is returned to the lubricant circulating system of theinternal combustion engine. In addition, the outer dimensions of ahydraulic pump can be desirably reduced by the combination with anaccumulator, in which configuration the accumulator is preferablyintegrated on the engine power section cover for avoiding separatepipes.

Furthermore, in order not to disadvantageously influence thedimensioning of important parts in the overall arrangement for thepurpose of an acceptable mounting process, the structural or assemblyunit according to the present invention further comprises a couplingelement of the adjusting system which is connected by a coupling rod andacts in an angle adjusting manner between the shaft and the drive wheel.Thus, a significant function unit of the overall device can beconstructed separately from the internal-combustion engine and can beintroduced into the assembly line of the internal-combustion engine.

It remains within the scope of the present invention to arrange thehydraulic pump also on the shaft which can be adjusted with respect toits angle of rotation, and to hold the pump housing to be non-rotatableon the cover side by way of a plug-in arrangement. It is alsoconceivable to arrange the linear pump, the hydraulic pump, possiblywith the generator wheel, and the control device formed of lines and thetiming valve in a separate part and to connect this part with the enginepower section cover. This development also permits the separatemanufacture of a function unit of the overall device. This developmentmay be used for a low-cost retrofitting.

BRIEF DESCRIPTION OF THE DRAWING

These and further objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of a presently preferred embodiment when taken inconjunction with the accompanying sole FIGURE which is a cross-sectionalaxial view of the adjusting device.

DETAILED DESCRIPTION OF THE DRAWING

A device designated generally by numeral 1 for adjusting the relativeangle of a camshaft 2 of an internal combustion engine (not shown indetail), with respect to a drive wheel 3 comprises an adjustingmechanism 4 and an actuating arrangement 5. The drive wheel 3 of theadjusting mechanism 4 is in a one-piece connection with a hollow hub 6which, by way of the periphery, is movable with respect to its angle ofrotation in a recess 7 on the outside of the shaft. Helical or a screwedgearing 8 allows the hollow hub 6 to interact with a coupling link 9which, in a recess 10 on the interior side of the camshaft, 2 via aslide bar 11, is non-rotatably connected with the camshaft 2. Foradjusting the relative angle of rotation of the camshaft 2 with respectto the drive wheel 3, the coupling link 9 can be axially displaced, inwhich construction a coupling rod 12 connects the coupling link 9 with ahydraulic linear motor 13 of the actuating arrangement 3.

The linear motor 13 is arranged in a detachably constructed engine powersection cover 14 and comprises essentially a cylinder 15 and a piston 16displaceable therein. A hydraulic pump 18 with a pump rotor 19,configured here as a radial piston pump, is arranged coaxially withrespect to the longitudinal or adjustment axis 17 of the linear motor 13on the engine power section cover 14 on the shaft side, in whichconfiguration the pump rotor 19 is arranged to be rotatably movable onthe periphery of the cylinder 15 of the linear motor 13. The hydraulicpump 18 is preferably provided as a radial piston pump which is actedupon on the inside. The pump 18 has a pump housing 20 which isconstructed in the engine power section cover 14, is open on the shaftside and receives the pump rotor 19, which is in a shaft-side drivingconnection, by way of a plug-in arrangement 21. For achieving astructural or assembly unit which has manufacturing advantages and isformed of the linear motor 13, the hydraulic pump 18 and the enginepower section cover 14, the engine power section cover 14 has a stepbore 22 for receiving a separate cylinder 15 of the linear motor 13which is constructed with different outside diameters. The cylinder 15arranged in the step bore 22, on the shaft side, is equipped with aflanged bush 23 for the slidably movable bearing of the pump rotor 19receiving radially displaceable delivery pistons 24. The flanged bush 23has intake-side and delivery-side control openings arranged to bedistributed along the periphery for the connection with inflow andoutflow chambers 25 and 26 arranged in the cylinder wall. The inflowchamber 25 and the outflow chamber 26 are each connected with anessentially axially directed respective duct 27 and 28 arranged in thecylinder wall. Each duct 27, 28, by way of a circumferential grooveconstructed on the periphery of the cylinder 15 of the linear motor 13,is connected with a pipe 29 and 30 arranged in the engine power sectioncover 14. The intake duct 27 and the delivery duct 28 are closed on theshaft-side end of the cylinder 15 of the linear motor 13 by a flangednut 31 which, with its outer edge area, is used for the axially securingthe flanged bush 23 for the pump rotor 19 on the cylinder 15.

The pump housing 20, which is open on the shaft side and arrangedeccentrically with respect to the longitudinal or adjusting axis 17 ofthe linear motor 13 in the engine power section cover 4, is equippedwith a sliding ring 32 which interacts with the delivery piston 24 andis axially secured by a generator wheel 33 arranged with axial play inthe plug-in arrangement 21. The generator wheel 33 may be a separatecomponent but it may also be constructed in one piece with the pumprotor 19. Preferably each generator wheel 33 interacts with a generator(not shown) which is arranged in the engine power section cover 14.

In order to avoid a separate hydraulic circuit for the hydraulicactuating arrangement 5, the intake pipe 29 in the engine power sectioncover 14 is connected with the lubricant circulating system of theinternal-combustion engine (not shown in detail). Furthermore, twopressure pipes 30 and 30' provided in the engine power section cover 14for acting on both sides of a piston 16, e.g. a differential piston, ofthe linear motor 13, which is constructed with different surfaces, arecontrolled by a timing valve 34. An annulus 38 provided between thecontrol pistons 35 and 36 of the control rod 37 of the timing valve 34can be connected with a discharge pipe 39 leading out on the machineside.

The timing valve 34 is connected with a preferablycharacteristic-diagram-controlled control device by way of which thecamshaft 2, for each operating point of the internal-combustion engine,is adjusted in its angle of rotation with respect to the drive wheel andthe adjusting angle is held which is determined for the respectiveoperating point. In order to be able to use a hydraulic pump 18 for sucha control that has a relatively small size because of the limited space,an accumulator 40 may be arranged on the engine power section cover 14which, via a connecting pipe 41, is in a medium-carrying connection withthe circumferential groove assigned to the pressure duct 28 in thecylinder wall.

In order to facilitate the mounting of the device 1 for adjusting therelative angle of rotation of the camshaft 2 with respect to the drivewheel 3, the structural or assembly unit, which comprises the actuatingarrangement 5 with the linear motor 13 and the hydraulic pump 18 as wellas the engine power section cover 14, may also comprise the couplinglink 9 of the adjusting mechanism 4 which is connected via the couplingrod 12 and adjusts the angle between the camshaft 2 and the drive wheel3. This avoids additional assembly measures for the device 1 arranged onthe internal-combustion engine.

Within the scope of the present invention, the hydraulic pump may alsobe arranged on the shaft with the adjustable angle of rotation, and thepump housing of the hydraulic pump may be held non-rotatably on the sideof the cover by a plug-in arrangement. In addition, it may also beprovided within the scope of the invention that the linear motor, thehydraulic pump--possibly with the generator wheel--and a control devicecomprising the timing valve with the lines are arranged in a separatepart which can be connected with the engine power section cover. In thisconfiguration, the separate part may serve as a retrofit kit.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

I claim:
 1. A device for adjusting a relative angle of rotation of ashaft with respect to a drive wheel, particularly the camshaft of aninternal combustion engine,comprising a hydraulic linear motorconstituting an actuating arrangement which acts upon an adjustingmechanism acting between the drive wheel and the shaft, wherein ahydraulic pump with a pump rotor is operatively arranged coaxially withrespect to one of a longitudinal and adjustment axis of the linearmotor.
 2. A device according to claim 1, whereinthe linear motor and thehydraulic pump are arranged coaxially to the shaft with the adjustableangle of rotation on a detachably constructed engine power sectioncover, and together therewith form a structural or assembly unit.
 3. Adevice according to claim 1 characterized in that the hydraulic pump isa radial piston pump.
 4. A device according to claim 1, wherein thelinear motor is a cylinder/piston unit.
 5. A device according to claim3, wherein the radial piston pump is arranged on the engine powersection cover on the shaft side, andthe pump rotor is disposed in arotatably movable manner on the periphery of the cylinder of the linearmotor cylinder/piston unit.
 6. A device according to claim 3, whereinthe radial piston pump is provided which is acted upon on the inside andhas a pump housing constructed in the engine power section cover, isopen on the shaft side andreceives the pump rotor which, by way of aplug-in arrangement, is in a shaft-side driving connection.
 7. A deviceaccording to claim 4, wherein a separate cylinder of the linear motor,which is constructed with different outside diameters, is arranged in astep bore of the engine power section cover, andthe cylinder, on theshaft side, is equipped with a flanged bush for the slidably movablebearing of the pump rotor which receives radially displaceable deliverypistons, and the flanged bush has intake-side and delivery-side controlopenings distributed along the periphery for connection with arespective inflow and outflow chamber arranged in the cylinder wall. 8.A device according to claim 7, wherein the inflow chamber and theoutflow chamber are each connected with an essentially axially directedduct arranged in the cylinder wall, andeach duct, by way of acircumferential groove constructed on a periphery of the cylinder of thelinear motor cylinder/piston unit is connected with a pipe arranged inthe engine power section cover.
 9. A device according to claim 8,wherein, on the shaft-side end, a flanged nut closes off the intake ductand the delivery duct and is assigned to the cylinder of the linearmotor,said flanged nut, with its outer edge area, being used for axiallysecuring the flanged bushing on the cylinder.
 10. A device according toclaim 6, wherein a generator wheel is operatively associated with axialplay to the pump housing open on the shaft side.
 11. A device accordingto claim 10, wherein the generator wheel is in one piece with the pumprotor.
 12. A device according to claim 8, wherein the pipe in the enginepower section cover is connected with a lubricant circulating system ofthe engine.
 13. A device according to claim 2, wherein pressure pipesprovided in the engine power section cover for two-sided acting upon apiston of the linear motor configured with different surfaces, arecontrolled by a timing valve,an annulus provided between control pistonsof a control rod of the timing valve being operatively connected with adischarge pipe leading out on the machine side.
 14. A device accordingto claim 8, wherein an accumulator is arranged on the engine powersection cover which,by way of a connecting line, is connected in amedium-carrying manner with the circumferential groove assigned to theduct in the cylinder wall.
 15. A device according to claim 2, whereinthe structural or assembly unit comprising the actuating arrangementwith the linear motor and the hydraulic pump as well as the engine powersection cover comprises a coupling link of the adjusting mechanism whichis connected by way of a coupling rod and adjusts the angle between theshaft and the drive wheel.
 16. A device according to claim 1, whereinthe hydraulic pump is arranged on the shaft with the adjustable angle ofrotation, and the pump housing is non-rotatably held on the cover sideby a plug-in arrangement.
 17. A device according to claim 1, wherein thelinear motor, the hydraulic pump and a control device are arranged in aseparate part which can be connected with the engine power sectioncover.
 18. A device for adjusting the relative angle of rotation of acamshaft with respect to a drive wheel of an internal combustionengine,comprising a linear hydraulic motor configured as an actuatingarrangement which is operatively associated with an adjusting mechanismacting between the drive wheel and the camshaft, and a piston pumparranged coaxially with respect to one of a longitudinal and adjustingaxis of the linear hydraulic motor and has a reciprocating piston whichis penetrated in the center by a cylinder of the linear hydraulic motor.